intel_mid_dma: add support for single item scatter-gather list

Current driver's device_prep_slave_sg can't be used by DMAC2 even
the sg list contains one item, this patch will enable DMAC2 to
use this API.
Signed-off-by: NFeng Tang <feng.tang@intel.com>
Acked-by: NVinod Koul <vinod.koul@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/intel_mid_dma.c

@@ -664,11 +664,20 @@ static struct dma_async_tx_descriptor *intel_mid_dma_prep_memcpy(
 	/*calculate CTL_LO*/
 	ctl_lo.ctl_lo = 0;
 	ctl_lo.ctlx.int_en = 1;
-	ctl_lo.ctlx.dst_tr_width = mids->dma_slave.dst_addr_width;
-	ctl_lo.ctlx.src_tr_width = mids->dma_slave.src_addr_width;
 	ctl_lo.ctlx.dst_msize = mids->dma_slave.src_maxburst;
 	ctl_lo.ctlx.src_msize = mids->dma_slave.dst_maxburst;
 
+	/*
+	 * Here we need some translation from "enum dma_slave_buswidth"
+	 * to the format for our dma controller
+	 *		standard	intel_mid_dmac's format
+	 *		 1 Byte			0b000
+	 *		 2 Bytes		0b001
+	 *		 4 Bytes		0b010
+	 */
+	ctl_lo.ctlx.dst_tr_width = mids->dma_slave.dst_addr_width / 2;
+	ctl_lo.ctlx.src_tr_width = mids->dma_slave.src_addr_width / 2;
+
 	if (mids->cfg_mode == LNW_DMA_MEM_TO_MEM) {
 		ctl_lo.ctlx.tt_fc = 0;
 		ctl_lo.ctlx.sinc = 0;
@@ -746,8 +755,18 @@ static struct dma_async_tx_descriptor *intel_mid_dma_prep_slave_sg(
 	BUG_ON(!mids);
 
 	if (!midc->dma->pimr_mask) {
-		pr_debug("MDMA: SG list is not supported by this controller\n");
-		return  NULL;
+		/* We can still handle sg list with only one item */
+		if (sg_len == 1) {
+			txd = intel_mid_dma_prep_memcpy(chan,
+						mids->dma_slave.dst_addr,
+						mids->dma_slave.src_addr,
+						sgl->length,
+						flags);
+			return txd;
+		} else {
+			pr_warn("MDMA: SG list is not supported by this controller\n");
+			return  NULL;
+		}
 	}
 
 	pr_debug("MDMA: SG Length = %d, direction = %d, Flags = %#lx\n",
@@ -758,6 +777,7 @@ static struct dma_async_tx_descriptor *intel_mid_dma_prep_slave_sg(
 		pr_err("MDMA: Prep memcpy failed\n");
 		return NULL;
 	}
+
 	desc = to_intel_mid_dma_desc(txd);
 	desc->dirn = direction;
 	ctl_lo.ctl_lo = desc->ctl_lo;